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Re: [PATCH v2] mips/malta: pass RNG seed to to kernel via env var


From: Peter Maydell
Subject: Re: [PATCH v2] mips/malta: pass RNG seed to to kernel via env var
Date: Tue, 4 Oct 2022 11:53:22 +0100

On Tue, 4 Oct 2022 at 11:40, Jason A. Donenfeld <Jason@zx2c4.com> wrote:
>
> And just to give you some idea that this truly is possible from firmware
> and I'm not just making it up, consider this patch to U-Boot:
>
> u-boot:
> diff --git a/arch/mips/lib/bootm.c b/arch/mips/lib/bootm.c
> index cab8da4860..27f3ee68c0 100644
> --- a/arch/mips/lib/bootm.c
> +++ b/arch/mips/lib/bootm.c
> @@ -211,6 +211,8 @@ static void linux_env_legacy(bootm_headers_t *images)
>                 sprintf(env_buf, "%un8r", gd->baudrate);
>                 linux_env_set("modetty0", env_buf);
>         }
> +
> +       linux_env_set("rngseed", 
> "4142434445464748494a4b4c4d4e4f505152535455565758595a5b5c5d5e5f60");
>  }
>

>
> So, as you can see, it works perfectly. Thus, setting this in QEMU
> follows *exactly* *the* *same* *pattern* as every other architecture
> that allows for this kind of mechanism. There's nothing weird or unusual
> or out of place happening here.

I think the unusual thing here is that this patch isn't
"this facility is implemented by u-boot [commit whatever,
docs whatever], and here is the patch adding it to QEMU's
handling of the same interface". That is, for boards like
Malta the general expectation is that we're emulating
a piece of real hardware and the firmware/bootloader
that it would be running, so "this is a patch that
implements an interface that the real bootloader doesn't
have" is a bit odd.

thanks
-- PMM



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